There are many situations where one wishes to isolate one or more components of a liquid sample. For example, with testing of biological samples for the presence of a particular analyte, e.g. in clinical diagnostic testing, the initial biological sample, such as blood, is often subjected to one or more processes designed to separate and/or enrich a particular fraction of the initial sample from the remaining components of the sample. For example, depending on the assay to be performed one may be interested in separating a certain cellular population or component thereof, such as cellular organelles, polynucleic acids, proteins and the like, from the remaining components of the sample.
With polynucleic acids such as DNA and RNA, there are many techniques currently available for the isolation of these components from biological samples such as blood. Generally, these techniques include disruption of cells with a detergent solution, followed by extraction of nucleic acids with organic solvents. Other methods use temperature extremes (boiling or freeze-thawing the biological sample) in order to extract the nucleic acids. These procedures are generally performed manually, with reagents taken repeatedly from a single, common source.
Current procedures for the isolation of polynucleic acids suffer from two important disadvantages. First, the technician is potentially exposed to biohazardous materials from the formation of aerosols and/or droplets resulting from repeated opening and closing of the specimen container and from waste material formed from the extraction process. Second, taking repeated aliquots from a single source of a reagent can result in contamination. Cross-contamination also occurs when the technician's gloves become contaminated from repeated opening and closing of the specimen tube. When PCR is used to amplify purified DNA, cross-contamination is clearly unacceptable.
Accordingly, there is a need for the continued development of devices which provide for the simple isolation of a one or more components of a sample. In particular, there is a need for the development of devices for use in the isolation of polynucleic acids which minimize the risk of exposure of the user to reagents and/or sample and do not suffer from the problems of cross contamination inherent in devices and methodologies which use reagents from a single source.
Relevant Literature
U.S. Patents describing DNA isolation devices include: U.S. Pat. Nos. 4,863,582; 5,188,963; 5,217,593; 5,229,297; 5,330,916; 5,334,499 and 5,346,999. Maniatis et al., Molecular Cloning: A Laboratory Manual (1988)(Cold Spring Harbor Press), 9.14-9.23 and the references cited therein provide a review of techniques for isolating high-molecular weight DNA from mammalian cells. Maniatis et al., supra, pp 7.84-7.85 and the referneces cited therein describe techniques for isolating RNA from human tissues. Other references of interest include: Taylor et al., A.J.C.P. (1990)93:749-753; Wahlberg et al., Electrophoresis (1992) 13: 547-551; Mischiati etal., Biotechniques (1993) 15: 146-151; Mischiati et al., J. Biochem. Biophys. Methods (1994) 28: 185-193; Fisher et al., Anal. Biochem. (1991) 194:309-315; Kepperud et al., Applied & Environrnental Microbiology (1993)59: 2938-44; Ramirez-Solis et al., Anal. Biochem. (1992) 201:331-335; Taylor et al., Am. J. Clin. Path. (1990) 93:749-753; Merel et al., Clin. Chem. (1996) 42:1285-1286; Boom et al., J. Clin. Microbiology (1990) 28: 495-503; Cheung et al., J. Clin. Microbiology (1994) 32:2593-2597; Casas et al., J. Virological Methods (1995) 53: 25-36; Muir et al., J. Clin. Microbiology (1993) 31: 31-38; Chomczynski et al., BioTechniques (1997) 22: 550-553; and Deggerdal & Larsen, Biotechniques (1997) 22: 554-557.